Conformational analysis of saturated heterocyclic

Application of NMR spectroscopy to heterocyclic chemistry has developed very rapidly during the past 15 years, and the technique is now used almost as routinely as H NMR spectroscopy. There are four main areas of application of interest to the heterocyclic chemist (i) elucidation of structure, where the method can be particularly valuable for complex natural products such as alkaloids and carbohydrate antibiotics (ii) stereochemical studies, especially conformational analysis of saturated heterocyclic systems (iii) the correlation of various theoretical aspects of structure and electronic distribution with chemical shifts, coupling constants and other NMR derived parameters and (iv) the unravelling of biosynthetic pathways to natural products, where, in contrast to related studies with " C-labelled precursors, stepwise degradation of the secondary metabolite is usually unnecessary. 

Conformational Analysis of Saturated Heterocyclic Six-Membered Rings... 

Conformational analysis of saturated heterocyclic six-membered rings 04AHC(86)41. 

Conformational Analysis of Saturated Heterocycles. LIV. The Conformation of Piperidine as Determined by Paramagnetic Shifts in the NMR, 1. D. 

Brown MD, Cook MJ, Hutchinson BJ, Katritsky AJ (1971) Conformational analysis of saturated heterocycles. XL. Stereochemistry of base-catalyzed hydrogen-deuterium exchange of methylene protons alpha to a sulfonyl group. Tetrahedron 27 593-600... 

Jones, R. A. Y, Katritzky, A. R., Snarey, M. (1970). The conformational analysis of saturated heterocycles. Part XXrV. Hexahydro-l,3,5-triazines. Journal of the Chemical Society B Physical Organic, 135-138. 

Conformation analysis of saturated six-member 0-heterocycles 98AHC (69)217. 

The best method used in the conformational analysis of saturated six-membered heterocyclic rings in the solid state is single-crystal X-ray structural analysis. The conformation in solution is not always identical. For solutions, H NMR spectroscopic analysis has been employed widely in the field of conformational analysis. The following methods deserve special mention. 

Conformational Analysis of Saturated Six-Membered Oxygen-Containing Heterocyclic Rings Erich Kleinpeter... 

Conformational analysis of saturated fused 1,3-heterocycles 92ACH107. 

Conformational analysis of N-heterocycles, general aspects 83IZV2432. Conformational equilibria of six-membered saturated N-heterocycles ... 

The conformational analysis of saturated five- and six-membered heterocycles, presenting data relevant to the carbohydrate field, has also been extensively reviewed. ... 

Configurational and conformational analysis of saturated heterocychc rings such as piperidine, a six-membered heterocyclic ring, and azepine, a seven-membered heterocychc ring, was carried out and is explained here in detail. 

Conformational Analysis of Five- and Six-Membered Rings and Related Non-Bridged Systems (Saturated Heterocyclic) , F. G. Riddell, in Aliphatic, Alicyclic and Saturated Heterocyclic Compounds , ed. W. Parker, Royal Society of Chemistry, London, 1974, vol. 1, pt. 3, pp. 69-91. 

Wilier, R.L. and Eliel, E.L., Conformational analysis. 34. Carbon-13 nuclear magnetic resonance spectra of saturated heterocycles. 6. Methylthianes, J. Am. Chem. Soc., 99, 1925, 1977. 

Bernath (92MI107) reviewed the synthesis and conformational analysis of these condensed-skeleton saturated heterocycles. 

Conformational analysis of 6-membered saturated S-heterocycles 89ACR357. 

Saturated six-membered N-heterocycles, conformational analysis of 8IAG567. 

We have covered a lot of ground in this chapter, and have used the huge topic of saturated heterocycles to explain a lot, not just about the reactivity and conformation of rings. Many of these explanations involved consideration of the alignment of orbitals— we called these stereoelectronic effects. The same analysis allowed us to make sense of the NMR spectra, and in particular the coupling constants, of cyclic molecules, both heterocycUc and carbocyclic. And by thinking about symmetry in these cyclic molecules we were also able to deduce the origins of symmetry-related features (such as diastereotopic protons) in the NMR spectra of acycUc compounds. 

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